The embargo against cuba did nto really start until the 1960s, before then there were arms embargoes.
It did start as you mentioned after Cuba seized a few US companies assets, US did a minor embargo, Cuba went in seized all other companies and the US started embargoing most trade.
Since then the embargo has been attempted to be lifted but the political backlash from Florida and a decent amount of voters in the rest of the US has stopped it. With Fidel gone and the communist threat basically dead it is now just the voters in florida, and sugar producers who really care about it.
As for all those properties that is something that is being discussed now and will have to be decided upon. Another major problem is going to be who owns the trademark names to various products. For example Bacardi, now USA but originally cubian, has trademarks they say they own while a company in Cuba also claims it; while there is an embargo and neither company can sell in other place it is meanless legal fight once the embargo is gone now it is a major international legal dispute.